mmc: sdhci-omap: Fix build if CONFIG_PM_SLEEP is not set

Commit f433e8aa ("mmc: sdhci-omap: Implement PM runtime functions")
combined the use of runtime PM and system suspend functions but left the
ifdef CONFIG_PM_SLEEP in place causing undeclared identifier error for
sdhci_omap_runtime_suspend if CONFIG_PM_SLEEP is not enabled.

Let's fix the error by removing ifdef CONFIG_PM_SLEEP and tagging the
reset of the PM related functions with __maybe_unused.

Let's also remove the forward declaration for sdhci_omap_context_save(),
that was accidentally left from an earlier version and is no longer used.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
[Ulf: Rebased and fixed build error]
Link: https://lore.kernel.org/r/20211021134352.10135-1-tony@atomide.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-omap.c

@@ -1415,8 +1415,9 @@ static int sdhci_omap_remove(struct platform_device *pdev)
 
 	return 0;
 }
-#ifdef CONFIG_PM_SLEEP
-static void sdhci_omap_context_save(struct sdhci_omap_host *omap_host)
+
+#ifdef CONFIG_PM
+static void __maybe_unused sdhci_omap_context_save(struct sdhci_omap_host *omap_host)
 {
 	omap_host->con = sdhci_omap_readl(omap_host, SDHCI_OMAP_CON);
 	omap_host->hctl = sdhci_omap_readl(omap_host, SDHCI_OMAP_HCTL);
@@ -1427,7 +1428,7 @@ static void sdhci_omap_context_save(struct sdhci_omap_host *omap_host)
 }
 
 /* Order matters here, HCTL must be restored in two phases */
-static void sdhci_omap_context_restore(struct sdhci_omap_host *omap_host)
+static void __maybe_unused sdhci_omap_context_restore(struct sdhci_omap_host *omap_host)
 {
 	sdhci_omap_writel(omap_host, SDHCI_OMAP_HCTL, omap_host->hctl);
 	sdhci_omap_writel(omap_host, SDHCI_OMAP_CAPA, omap_host->capa);